It is known in the automotive industry to provide a vehicle space frame which can be used to mount various components and body panels for the motor vehicle. Typically, the space frame is made from many frame structures which are joined together by welding or other types of connections. The numerous connections that are typically required to form a space frame from the frame structures leads to tolerance build-up, which causes dimensional accuracy problems in the space frame.
It is an object of the invention to provide a space frame that requires fewer parts and fewer connections than the conventional space frame, so that a space frame of greater dimensional accuracy can be produced.
In accordance with this object, the present invention provides a space frame for a motor vehicle, comprising a first hydroformed, longitudinally extending tubular lower side rail member, and a second hydroformed, longitudinally extending tubular lower side rail member, the lower side rail members being laterally spaced from one another. Also included is a pair of hydroformed tubular upper longitudinal members, each being an integrally formed member fixed to an associated one of the lower side rail members. The structure of each upper longitudinal member includes a longitudinally extending portion constructed and arranged to support a roof of the motor vehicle, each longitudinally extending portion extending longitudinally between an upper end of an A-pillar structure provided by the space frame and an upper end of a rearward-most pillar structure of the space frame. The hydroformed tubular upper longitudinal members thus define lengths between the vehicle A-pillar structures and the rearward-most structures of the space frame. Laterally extending connecting structure connects the lower side rail members to one another.
The object of the present invention can be achieved by other structural components, as well as various method of manufacture. For example, in one method of the invention, the following steps are performed: placing a tubular metal blank having a generally U-shaped configuration into a hydroforming die assembly, the die assembly having die surfaces defining a die cavity; providing pressurized fluid to an interior of the tubular metal blank so as to expand the blank into conformity with the die surfaces of the die cavity and thereby form a U-shaped hydroformed cross member; positioning first and second lower side rail members in laterally spaced relation to one another; connecting a first end of the hydroformed cross member to the first lower side rail member; and connecting a second end of the hydroformed cross member to the second lower side rail member.
Because fewer parts are required in accordance with the space frame of the present invention, assembly is made much simpler.